The proposed research for the period of 9-1-75 to 8-31-76 includes the following: (1) As a preliminary approach to evaluating the functional significance of the topographic features of the projection from the cerebral cortex to the striatum (caudate nucleus and striatum), the effects on motor behaviour of selective striatal lesions will be studied. Noteworthy is the use of evoked gross or focal potentials to stimulation of the cortex during aseptic surgery to allow accurate definition of the specific "input zone" of the striatum to be destroyed. (2) We have now shown that cortico-striatal evoked electrical responses allow accurate definition of the topographic features of the cortico- striatal projection. A second goal is to stimulate specific regions of the striatum and record responses in the globus pallidus. It is hoped that these studies will provide a clearer picture of the overall topographic features of the input-output organization of the striatum. (3) A third study, which will follow the second proposed study, is an evaluation of effects of selective lesions in the globus pallidus on motor behavior. These lesions will damage specific "input zones" of the pallidum (e.g., area "x" of cerebral cortex yields region "y" of striatum yields region "z" of globus pallidus). Electrophysiological recordings will provide precise stereotaxic definition of the region to be damaged.